如何获得具有多个表关系的单行记录？

Question

Table 1 : User_Profile

-------------------------------------------------------------------------------------------
User_profile_id   | Profile_form_id |   Email       |   Zipcode   |   Firstname | Lastname
-------------------------------------------------------------------------------------------

1                 | 4               |john@gmail.com |  123456     |  john       | peter 
------------------------------------------------------------------------------------------

-

Table 2 : Profile_attribute_form

-------------------------------------------------------------------
profile_attribute_id   | Profile_attribute_name |  profile_form_id 
-------------------------------------------------------------------

1                      | Address                |  4
-------------------------------------------------------------------
2                      | Phone Number           |  4
------------------------------------------------------------------
3                      | City                   |  4
-------------------------------------------------------------------

Table 3 : User_Profile_attribute

---

User_profile_id        | Profile_attribute_id   |  profile_attribute_value 
--------------------------------------------------------------------------

1                      | 1                      |  23,Times road
--------------------------------------------------------------------------
1                      | 2                      |  9786530874
--------------------------------------------------------------------------
1                      | 3                      |  New York
--------------------------------------------------------------------------

Needed Final Result :

-------------------------------------------------------------------------------------------
User_profile_id|Profile_form_id|Email |Zipcode|Firstname|Lastname|Address|PhoneNumber|City
-------------------------------------------------------------------------------------------

1              |4              |gm.com|123456 |john     |peter   |addr1  |9786530874 |NewY 
-------------------------------------------------------------------------------------------

How to i build the mysql query for the above result.

Answer 1

You are need to do is JOIN the tables and then PIVOT the data. However MySQL does not have a PIVOT function but you can replicate the functionality using an aggregate function and a CASE statement.

If you know the values to turn into columns then you can use the following:

select up.user_profile_id,
  up.profile_form_id,
  up.email,
  up.zipcode,
  up.firstname,
  up.lastname,
  min(case when paf.Profile_attribute_name= 'Address' 
            then upa.profile_attribute_value end) as Address,
  min(case when paf.Profile_attribute_name= 'Phone Number' 
            then upa.profile_attribute_value end) as PhoneNumber,
  min(case when paf.Profile_attribute_name= 'City' 
            then upa.profile_attribute_value end) as City
from user_profile up
left join Profile_attribute_form paf
  on up.Profile_form_id = paf.Profile_form_id
left join User_Profile_attribute upa
  on paf.profile_attribute_id = upa.Profile_attribute_id
  and up.User_profile_id = upa.User_profile_id
group by up.user_profile_id,
      up.profile_form_id,
      up.email,
      up.zipcode,
      up.firstname,
      up.lastname

see SQL Fiddle with Demo

Now if you want to perform this dynamically, meaning you do not know ahead of time the columns to transpose, then you should review the following article:

Dynamic pivot tables (transform rows to columns)

Your code would look like this:

SET @sql = NULL;
SELECT
  GROUP_CONCAT(DISTINCT
    CONCAT(
      'min(case when paf.Profile_attribute_name = ''',
      paf.Profile_attribute_name,
      ''' then upa.profile_attribute_value end)  AS ',
      replace(paf.Profile_attribute_name, ' ', '')
    )
  ) INTO @sql
from user_profile up
left join Profile_attribute_form paf
  on up.Profile_form_id = paf.Profile_form_id;

SET @sql 
  = CONCAT('select up.user_profile_id,
              up.profile_form_id,
              up.email,
              up.zipcode,
              up.firstname,
              up.lastname, ', @sql, '
           from user_profile up
           left join Profile_attribute_form paf
             on up.Profile_form_id = paf.Profile_form_id
           left join User_Profile_attribute upa
             on paf.profile_attribute_id = upa.Profile_attribute_id
             and up.User_profile_id = upa.User_profile_id
           group by up.user_profile_id,
                 up.profile_form_id,
                 up.email,
                 up.zipcode,
                 up.firstname,
                 up.lastname');

PREPARE stmt FROM @sql;
EXECUTE stmt;
DEALLOCATE PREPARE stmt;

see SQL Fiddle with Demo